Fan construction



Dec. 27, 1966 D. N. STEWART ET AL 3,294,315

FAN CONSTRUCTION Filed Spt. 28, 1964 m 4 \\\\\\\\\\.m I 2 zl I I 3 I m 7 u INVENTORS, Passe {Z OZS'on nd y Der/"e? 7?. 5220/42? ATTOPNEY:

United States Patent 3,294,315 FAN CONSTRUCTION Derrel N. Stewart, Hamburg, and Russell Olson, Buffalo, N.Y., assignors to Buffalo Forge Company, Bufialo, N.Y., a corporation of New York Filed Sept. 28, 1964, Ser. No. 399,608 4 Claims. (Cl. 230-134) The present invention relates to a fan construction and more particularly to an improved spark-resistant fan.

To avoid explosions in the pumping of gases which have combustible or explosive qualities, it is necessary to use spark-resistant fan constructions to prevent sparks from being struck as a result of the engagement between the blade tips and the conduit in which the blade rotates. In the past various types of constructions have been utilized for the foregoing purpose. One type was where the entire blade was made of spark-resistant nonferrous material, such as aluminum or brass. However, such constructions were extremely expensive and did not have the desirable strength qualities of ferrous materials. Another type of construction was a nonferrous liner in the duct in which the fan was located. However, the installation of such liners was not only costly but also was an inefficient solution because it created an uneven surface causing both turbulence and hang-up of foreign matter within the duct. It is with an improvement over the foregoing types of prior art devices for providing a spark-resistant fan construction that the present invention is concerned.

It is, accordingly, one of the objects of the present invention to provide an improved composite spark-resistant fan which is both highly efficient and which can be fabricated at a low cost. A related object of the present invention is to provide a spark-resistant fan construction which can be fabricated by merely securing a sparkresistant tip material to a blade "body in an extremely efficient manner without requiring subsequent metal finishing operations after the joining has been effected, thereby causing the cost of the fan to be relatively low.

A further object of the present invention is to provide an improved method of fabricating the improved sparkresistant fan of the present invention. Other objects and attendant advantages of the present invention will readily be perceived hereafter.

The improved composite unfinished spark-resistant blade construction of the present invention comprises a ferrous blade body having an inner end for attachment to a hub and an outer edge of a first cross sectional dimension and a nonferrous spark-resistant strip-like member joined to said outer edge of the blade body by a weld with the strip-like member originally having had a second cross sectional dimension which was slightly larger than the first dimension but which was caused to approach the first dimension in the area of the weld as a result of being heated during welding, to thereby cause the tip to merge uniformly with the outer edge of the blade and thus cause the area of the weld to not require any subsequent finishing operation, the striplike member also having an outer edge portion which is sufficiently remote from both the blade body and the area at the weld to remain substantially undistorted as a result of the heating of the strip for producing the weld, whereby the mere welding of the outer strip of nonferrous material to the blade body produces a completed construction without requiring any subsequent metal machining operations.

The improved method of fabricating the spark-resistant fan blade of the present invention comprises the steps of providing a ferrous blade body having a first cross sectional thickness at the outer edge portion thereof, placing an elongated nonferrous strip-like member in contiguous Patented Dec. 27, 1966 ice relationship to said outer edge portion of said blade body with the nonferrous strip-like member having a cross sectional thickness which is in excess of the cross sectional thickness of the outer edge portion of the blade body, the elongated nonferrous member and the blade body having melting temperatures which are sufiiciently close so as to prevent one from melting excessively when both are heated for joining them into a unitary body, and the additional step of heating both the elongated strip-like member and the outer edge portion of the blade body while both are in contiguous relationship to cause the fusion of one into the other with the heating causing the larger cross sectional dimension of the nonferrous strip-like member to be reduced and to substantially approach the thickness of the outer edge portion of the blade body to provide a smooth transition from the ferrous blade body to the nonferrous tip, and the nonferrous strip-like member being of a sufficient dimension axially of the blade body so that its outer edge portion remote from the blade body remains substantially undistorted as a result of heat produced during welding of the two members whereby the necessity for subsequent finishing operations of the joined members is obviated, thereby providing a spark-resistant fan construction in an economical manner. The present invention will be more fully understood when the following portions of the specification are read in conjunction with the accompanying drawings wherein:

FIGURE 1 is a side elevational view of a fan including a plurality of spark-resistant fan blades mounted on a hub;

FIGURE 2 is a front elevational view of the fan construction of FIGURE 1;

FIGURE 3 is a view taken substantially along line 4-4 of FIGURE 2 showing the orientation between the outer tip and the blade body before they are joined; and

FIGURE 4 is a view taken substantially along line 44 of FIGURE 2 showing the manner in which the outer spark-resistant tip portion of the blade merges into the blade body.

The improved spark-resistant fan 10 includes a hub 11 having mounted thereon blades 12, each of which consists of a ferrous blade body portion 13 and an outer nonferrous tip 14, as can be seen from FIGURES 1 and 2. Each blade body 12 has an inner edge (not numbered) which is secured to hub 11 and an outer edge 13' which mounts spark-resistant tip portion 14. Blade 10 is intended to rotate within ferrous duct 15.

It will readily be appreciated that if the entire blade consisting of blade body 13 and outer tip 14 were made of ferrous material, there could be sparking in the event that the outer tips of the blades struck duct 15 during rotating. This striking may be a common occurrence for various reasons.

In order to overcome sparking which may result from contact between the outer tips of blade bodies 12 and the inner surfaces of duct 15, nonferrous tips 14 are welded to blade bodies 13 to provide the composite structure shown in cross section in FIGURE 4. Nonferrous tip 14, in its preferred form, before joining to blade body 13 comprises a circular rod 14' of nonferrous material (FIGS. 2 and 3) and it has a larger cross sectional dimension than the cross sectional dimension of blade body 13 at the outer edge portion 13' thereof. While rod 14 has been shown as being of circular cross sectional configuration, it will be appreciated that other suitable cross sectional configurations may be used. Nonferrous rod 14 may be made of a bronze alloy. A bronze alloy known by the trademark Everdur of the American Brass Co., and having a grade designation of Anaconda 1010 has been used successfully. The blade body 13 is preferably mild steel.

During the process of fabrication, the rod 14' is laid in contiguous relationship relative to outer edge portion 13 and both are subjected to a heat as a result of a tungsteninert-gas type of welding which causes fusion of one into the other and causes them to assume the finished configuration shown in FIGURE 4. The tungsten-inert-gas type of welding provides an arc in excess of the melting temperatures of both blade body 13 and rod 14, it being noted that the melting temperatures of both the blade body and the tip .are sufficiently close so that one does not run before the other one is heated up to sufficient fusion temperature. In this respect, the melting point of the ferrous blade body is approximaately 2550 F. and the rod 14 is approximately 1830 F.

As a result of the application of heat during the welding process, the larger cross sectional dimension of rod 14 reduces and merges toward the smaller cross sectional dimension of blade body 13 to provide a smooth transition in size between the outer tip 14 (FIG. 4) and blade body 13 in the area of weld 16. Because there is such a smooth transition, a subsequent metal finishing operation in the area of the weld 16 is not required thereby maintaining the cost of the blade relatively low. In addition the smooth merging causes the blade to have a relatively high efficiency. Due to the fact that in the embodiment shown the outer tip 14 is at least as thick as the blade 13, the outer tip is highly damage-resistant in the sense that the outer tip will not be greatly damaged in the event that it does strike the duct 15. Preferably the ouer tip should be thicker than the blade body, as shown in FIG. 4, said increased thickness enhancing the damage resistance characteristic.

It is also to be noted that the outer edge 17 of outer tip 14 (FIGS. 2 and 4) retains its rounded configuration even after the welding has been completed. The reason for this is that there is a sutficiently large distance between this outer edge and the area of the weld so that the heat applied during welding does not cause outer edge 17 to become distorted. Because of this, no finishing or smoothing operation is required at the outer tip 17 of the blade, thereby further reducing the cost of the blade construction.

It can be seen from FIGURE 2 that originally rod 14 is longer than the outer edge 13 of blade body 13. It will also be apprecicated that since rod 14 is longer than outer edge 13' of the blade body 13, it can be grasped for manipulation into conforming relationship with outer edge 13 in the event that the welding is to be effected manually. After the welding has been completed, rod 14' is severed from the ti portion 14 at 18 in FIGURE 2. It will be appreciated that both ends of each striplike outer tip 14 may be ground or otherwise smoothed at 18 after the welding has been completed and that the obviating of metal finishing operations referred to above related only to the elongated welded area between rod 14' and edge 13 of blade body 13.

The tungsten-inert-gas type of welding which is utilized in the present instance causes the composite blade construction to essentially approach a homogeneous construction where the outer tip and blade body both act as one and their separation due to mechanical forces normally encountered in fan operation is virtually impossible. The welding is preferably effected on both sides of the blade body.

It can thus be seen that the improved fan construction of the present invention is manifestly capable of achieving the above enumerated object of economy because the entire finishing operation of fabricating the composite blade consists of the mere welding of the outer nonferrous tip portion to the outer edge of the blade body, without more, and utilizing this welding process to provide the final desired cross sectional configuration, thereby obviating the necessity for metal working or metal finishing operations which increase the cost of the spark-resistant fan, inasmuch as the welding is not only utilized for joining a non-sparking material to a ferrous blade body but incidental to the joining function which it performs it shapes the tip to the required configuration without producing undesirable distortion.

While a preferred embodiment of the present invention has been disclosed, it will be appreciated that the present invention is not limited thereto but mamy be otherwise embodied within the scope of the following claims:

We claim:

1. A method of fabricating a spark-resistant fan blade comprising the steps of providing .a ferrous blade body having a first cross sectional thickness at the outer edge portion thereof, placing an elongated nonferrous strip-like member in contiguous relationship to said outer edge portion of said blade body, said nonferrous strip-like member having a portion of cross sectional thickness which is in excess of said cross sectional thickness of said outer edge portion of said blade body, said elongated nonferrous member and said blade body having melting temperatures which are sufficiently close so as to prevent one from melting excessively when both are heated for fusion into a unitary body, and heating both said elongated strip-like member and said outer edge portion of said blade body while both are in contiguous relationship to cause fusion of one into the other with said heating causing said portion of larger cross sectional thickness of said nonferrous elongated strip-like member to be reduced and substantially approach the thickness of said blade body to provide a smooth transition therebetween, said striplike nonferrous member being of sufiicient dimension axially of said blade body so that its outer edge portion remote from said blade body remains substantially undistorted from the heating resulting in the fusion of said elongated strip-like member.

2. A method of fabricating a spark-resistant fan blade as set forth in claim 1 wherein said strip-like member is of greater length than the outer edge of the blade body during the joining thereof to said outer edge of said blade body to provide a length of strip-like member beyond the edge of said blade body for facilitating the manipulation of said strip-like member into conforming engagement with said outer edge of said blade body during said joining, and the step of severing the portion of said strip-like member which extends beyond the portion which is joined to said outer edge of said blade body after the joining of said strip-like member to said blade body has been completed.

3. A composite spark-resistant blade construction comprising a ferrous blade body having an inner edge for attachment to .a rotatable hub and an outer edge adapted to be located adjacent a fixed casing, and a spark-resistant strip-like member joined to said outer edge of said blade body by a weld to thereby tend to obviate sparking in the event said strip-like member of said blade construction strikes said casing, said weld providing fusion of a portion of said strip-like member and said outer edge into each other for a substantial bonding zone in a direction axially of said blade body, and said strip-like member and said ferrous blade body having melting temperatures which are sufficiently close to each other to effect said fusion to produce said weld.

4. A method of fabricating a spark-resistant fan blade comprising the steps of providing a ferrous blade body having an outer edge portion, placing an elongated nonferrous strip-like member in contiguous relationship to said outer edge portion, said elongated nonferrous member and said blade body having melting temperatures which are sufficiently close so as to prevent one from melting excessively when both are heated for fusion into a unitary body, heating both said elongated strip-like member and said outer edge portion of said blade body when both are in contiguous relationship to cause fusion of one into the other to a substantial axial depth, said strip-like member having originally had a portion with a cross sectional dimension which was different from the cross sectional dimension of said outer edge portion of said blade body, and said heating causing said portion of different cross sectional dimension to be changed to substantially approach the cross sectional dimension of said outer edge portion of said blade body to provide a smooth transition therebetween incidental to said heating which effects said fusion.

References Cited by the Examiner UNITED STATES PATENTS 6 1,750,643 3/1930 Murray et a1 219-118 2,742,224 3/ 1956 Burhans 25 3-7 7 3,068,016 12/1962 Dega 277-96 5 FOREIGN PATENTS 572,059 9/ 1945 Great Britain. 733,918 7/1955 Great Britain.

10 MARK NEWMAN, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

3. A COMPOSITE SPARK-RESISTANT BLADE CONSTRUCTION COMPRISING A FERROUS BLADE BODY HAVING INNER EDGE FOR ATTACHMENT TO A ROTATABLE HUB AND AN OUTER EDGE ADAPTED TO BE LOCATED ADJACENT A FIXED CASING, AND A SPARK-RESISTANT STRIP-LIKE MEMBER JOINED TO SAID OUTER EDGE OF SAID BLADE BODY BY A WELD TO THEREBY TEND TO OBVIATE SPARKING IN THE EVENT SAID STRIP-LIKE MEMBER OF SAID BLADE CONSTRUCTION STRIKES SAID CASING, SAID WELD PROVIDING FUSION OF A PORTION OF SAID STRIP-LIKE MEMBER AND SAID OUTER EDGE INTO EACH OTHER FOR A SUBSTANTIAL BONDING ZONE IN A DIRECTION AXIALLY OF SAID BLADE BODY, AND SAID STRIP-LIKE MEMBER AND SAID FERROUS BLADE BODY HAVING MELTING TEMPERATURES WHICH 